1. Field of the Invention
The present invention relates generally to coupling systems adapted for use in trailer coupling arrangements and specifically to a fifth wheel coupling arrangement for use in coupling a tractor and trailer.
2. Description of the Prior Art
Trucks, sometimes referred to as “Tractor Units” or “Tractors”, are often coupled with trailers to move cargo stored on or in the trailer. Often, tractors are coupled to trailers by means of a “fifth-wheel” hitch assembly. This coupling assembly comprises a kingpin, a steel pin on the front of the trailer, and a horseshoe-shaped coupling device (yoke) mounted on the tractor. A surface of the trailer (“trailer plate” with the kingpin at the center) rotates against a surface of the yoke which does not rotate.
A special kind of tractor, sometimes called a “yard truck” is often used in terminals, such as intermodal terminals, in which trailers are moved from one place to another. A yard truck comprises a yoke coupled to a boom assembly. The boom assembly permits the yoke to be raised a desired distance such that the legs of the trailer are raised above the driving surface. This arrangement obviates the need to raise and lower the legs individually as when, for example, a conventional tractor is coupled to the trailer. This raising of the boom and corresponding raising of the trailer has the effect of raising the trailer's center of gravity. As some trailers are very heavy when filled with cargo, the higher center of gravity of a raised trailer may cause the trailer to be more susceptible to overturning than a trailer that is not raised with a fifth wheel boom.
Whether the trailer is raised or not, most tractors have a system in which the yoke closes around the neck of the kingpin to prevent the kingpin from uncoupling from the yoke. When properly engaged, this arrangement provides for secure coupling between the tractor and trailer. However, accidents often result from improper coupling between the kingpin and the yoke. Such accidents often result when the yoke “jaws” close when the kingpin is not positioned within the space between the jaws, for example when the kingpin is positioned above the yoke. This faulty coupling condition is known as a “top lock”.
Occasionally, the kingpin is properly positioned within the yoke, but the jaws fail to close properly around the kingpin such that the jaws and the kingpin are not locked in position. This faulty coupling condition is known as a “false lock”.
Other accidents occur when a trailer is moved when the trailer legs are still on the ground or in close proximity to the ground. This can occur when the operator either fails to raise the legs, or in the case of trailers moved by yard trucks, when the operator fails to raise the boom.
There have been a number of attempts to improve tractor trailer coupling arrangements by providing certain safety features. For example, U.S. Pat. No. 5,861,802, Hungerink, teaches an electronic coupling control system comprising a hitch plate movement sensor, a kingpin sensor, a lock sensor, and a system interface in which vehicle operation capabilities may be changed depending upon the sensor readings.
U.S. Pat. No. 5,477,207, Frame, discloses a fifth wheel coupling warning device comprising a proximity sensor which alerts an operator that the latching system is engaged or disengaged such that the operator can determine the state of the coupling system based solely on the signal provided by the warning device.
U.S. Pat. No. 5,625,335, Kelly, discloses a device for monitoring operation of a lock lever of a fifth wheel trailer hitch. U.S. Pat. No. 6,100,794, Hillier, et al. provides a fifth wheel coupling system comprising a detector for detecting when the pull handle is properly positioned in the locking position on the trailer kingpin. U.S. Pat. Nos. 6,285,278, 6,452,485, 7,548,155, Schutt et al. disclose a fifth wheel hitch electronic monitoring system comprising a trailer proximity sensor, a hitch plate movement sensor, a kingpin sensor, and a lock sensor, U.S. Pat. No. 6,587,041, Brown, teaches a system for sensing the presence of a connection between a tractor and trailer. U.S. Pat. Nos. 8,866,283 and 7,140,632, Alguera et al., provide a device for indicating the locking state of a fifth wheel coupling arrangement. U.S. Pat. No. 5,876,055, Fontaine provides an electronic induction switch system to indicate open and closed positions of the locking mechanism and to indicate whether the king pin is properly seated in the locking mechanism.
U.S. Pat. No. 7,253,721, Flohr et al., discloses a coupling monitoring system comprising one or two electronic control units, sensors for sensing a coupling condition of the electronic, mechanical, and/or hydraulic connection. Sensor signals are transmitted to an electronic control unit which, in response, prevents erroneous coupling or uncoupling and prevents drive-away of the vehicle or implement. U.S. Pat. No. 7,619,506, Knoll et al. provides an asset tracking system which comprises a sensor which detects whether a trailer is coupled with a tractor.
U.S. Pat. No. 7,825,783, Gallego, et al. teaches a device for detecting and displaying the position of components of vehicle couplings. U.S. Pat. No. 7,932,816, Schmidt, et al. discloses a device for detecting and displaying the position of vehicle couplings.
U.S. Pat. No. 7,967,319, Alguera, et al. provides a vehicle coupling aid comprising a sensor for detecting the locking of the coupling. U.S. Pat. No. 8,615,347 Alguera, Gallego, et al. provides an anti-theft security device for a vehicle coupling which prevents a semi-trailer from becoming decoupled without authorization.
US Patent Application No. 20080191449, Standen discloses a system comprising a sensor which produces an electrical signal proportional to the vertical distance between hitch assembly and the underside of the trailer.
What is needed is a coupling system which will permit a fifth wheel trailer to be easily connected and safely moved, particularly a system adapted for use by a yard truck moving trailers within a transportation terminal.